Rotary heads are used in manufacturing of cardboard boxes, cartons, cases and the like from sheets of cardboard. In the manufacture of cardboard boxes, the cardboard sheets are cut by trimming heads, slotted by slotting heads, and creased by scoring heads to form a blank. Ben the blank is folded, it forms a box, carton or case.
A rotary head assembly includes a pair of rotary heads (upper and lower) mounted on horizontally oriented rotatable shafts for trimming, slotting and scoring the cardboard and an axial alignment assembly for keeping the rotary heads in axial alignment. The cardboard moves through the space between the pairs of corresponding upper and lower rotary heads. In order to accurately trim, slot, or score the cardboard, the male blades of the rotary head must be perfectly aligned with the female recesses provided in the corresponding rotary head. If the male blade and female recess of the rotary heads are not aligned, the blades could hit other parts of the head and cause damage to the blade and to other parts of the head assembly as well as mutilate the cardboard sheet. Thus, axial alignment of the rotary heads for trimming, slotting, and scoring is a critical part of the cardboard blank forming operation.
When the size or shape of blanks changes, the rotary heads must be moved along their respective axes and aligned to accommodate such changes. The axial alignment assembly moves the rotary heads to the appropriate position and aligns the corresponding heads. The axial alignment assembly includes a motorized carriers mounted on corresponding parallel shafts, away from the area through which the cardboard is fed. For example, the upper rotary heads, located above the cardboard feed area, have their respective carriers and carrier shafts located above them while the lower rotary heads have their respective carriers and carrier shafts located below them. The axial alignment assembly also includes a yoke connected to the carrier. The yoke has outwardly extending arms. The arms extend on either side of the rotary, head shaft. The axial alignment assembly also includes guide plates fixed to the rotary heads and wear pads on at least one yoke arm for bearing against the guide plates which rotate with the rotary heads.
When the carrier moves axially along its shaft, the yoke and yoke arms engage the rotary head and move the rotary head axially. Once the carrier has moved the rotary head to the desired location, the carrier stops and thus locks the rotary head in a horizontal position. Once the upper and lower corresponding heads have been axially aligned relative to one another, it is critical that this alignment be maintained while the heads rotate during operation.
Axial alignment of the heads is at present accomplished by the use of rectangular metal wear pads mounted to the yoke arms. The wear pads contact the spaced-apart metal guide plates. As the head rotates, the spaced apart plates rotate and rub against the wear pads. The metal-to-metal contact between the guide plates and the wear pads causes accelerated wear in the wear pads and thus requires frequent replacement of the wear pads. Replacement of the wear pads is time consuming and costly because the entire axial alignment assembly must be disassembled in order to access the wear pads located between the yoke and the guide plates. When the wear pads are replaced, the upper and corresponding lower heads must be realigned as a result of changes in thickness of the wear pad. As a result of the present alignment system, cardboard manufacturers incur considerable time to complete the replacement and realignment procedure and expense in labor costs and machinery down time.
An alternative axial alignment system for rotary heads is disclosed in U.S. Pat. No. 4,926,730 issued to Garrett. The invention is directed to a yoke having a series of holes axially bored through the yoke arms. Roller bearings are mounted in the holes. The roller bearings have a diameter greater than the yoke thickness to insure contact with the head plates. During operation, the roller bearings perform the same function as the wear pads described above and rub against the guide plates as the guide plates rotate with the head. As the roller bearings begin to wear, they must be manually adjusted to maintain the desired alignment of the rotary heads. Manual adjustment of the roller bearings requires shutting down the machinery and separating the yoke from the guide plates attached to the rotary head. Similarly as with the replacement of the wear pads described above, replacement or adjustment of the roller bearings disclosed in Garrett is time consuming and costly to the cardboard blank manufacturer. Moreover, once the rollers in Garrett are adjusted or replaced, the upper and lower heads must be realigned. This additional step increases the time and cost of an already time consuming and costly alignment procedure.
In view of the axial alignment assemblies and methods at present available for axially aligning rotary heads, there is a need for an axial alignment assembly and method for aligning such rotary heads inexpensively.
There is a further need for an axial alignment assembly for rotary heads that is inexpensive to manufacture.
There is yet further need for an axial alignment assembly for rotary heads that requires little time to install or replace.
There is still a further need for an axial alignment assembly for rotary heads that is self-aligning.
There is a yet another need for an axial alignment assembly for rotary heads that may be used in existing head as assemblies.
There is still another need for an axial alignment assembly for rotary heads that may be made primarily of a self-lubricating material.
There is still yet a further need for a method of axially aligning, rotary heads that takes less time to install than present methods.